The corn to ethanol process is a matured technology and the enzyme (α-amylase and glucoamylase) needed for starch hydrolyses is commercially available. The production of ethanol becomes very difficult when lignocellulosic feed stocks (switchgrass, pinewood) are used. The sugars are locked in a very complex structure and so require costly enzymes to unlock the sugars. Among the research community, this is known as “recalcitrance” and such recalcitrance currently limits brewers to a 40% conversion of the energy content available in cellulosic feedstock to ethanol. If monomer sugars are readily available, the fermentation process, by contrast, converts about 90% of the energy in simple sugars to ethanol.